Wednesday, August 17, 2005

Penny wise and gallon foolish

Mr. Neutron has me thinking about math this afternoon and since we have been talking about gas milage in the comments from a post yesterday it reminded me of something I heard on the radio yesterday. A reporter was talking to people filling up their cars at local gas stations and asking them about the effect of the higher prices. One woman they spoke to said that she was using a lower grade, and therefore cheaper, gas as a result. I have long contended that most people, if not exactly dumb, do not really think very well. Assuming this woman normally uses the higher grade gas because it gives her better performance (as opposed to being required for her particular type of car) this is a perfect example of that. If she gets better milage from the higher octane fuel, opting for the lower octane version is the LAST thing she should do when prices go up. The difference in price between grades is usually a fixed constant amount, typically about 7 cents a gallon for mid grade and about 14 cents for high grade. (These are figures from memory since I am too lazy to run down the block to check the exact figures.) When gas is, say, $1.75 a gallon paying 7 cents more per gallon makes sense if it boosts you mpg by 4% or more. When the price goes up to $2.50 a gallon the mid grade is still only 7 cents more so it now makes sense to buy the higher grade if it increases the mpg by as little as 2.8%. The gain in performance is always a constant amount but the higher the price the less you pay, percentage wise, to get it.

Americans in general, and sadly for my profession, lawyers in particular, practically revel in their inability to do math. Even really simple math like the above. I've wanted to do a post on innumeracy, one of my (many) pet peeves for quite a while and when I finally do this will be one of the examples I use. That and people who need a little card to tell them what 20% of their restaurant bill is. People say, hee hee, I can't do math. Why isn't that just as embarrassing as saying, hee hee, I can't read?

8 Comments:

Assuming this woman normally uses the higher grade gas because it gives her better performance (as opposed to being required for her particular type of car)

Says here and here (and about a zillion other pages if you Google "octane mileage") that higher octane probably doesn't mean better mileage, especially if your car is relatively new. In fact, there's a very good chance that it means lower mileage. Match the fuel to the engine for best results.

I have always wondered if the higher grade actually gave you better milage, tho I assumed it did. I had planned someday to run a test in my own car to see if I could find a significant difference. I guess I could have just looked it up. Or better yet, just ask Joseph to do it. All that said, if the woman in question is now using a grade of gas that is not recomended for her car she may still be money in the hole in the long run with the problem still becoming relatively worse as the price increases.

Do you want to know why some people can't do math? Well, some people are just lazy. But with that out of the way, there is little to no extra effort put toward people who have trouble with math. If you have trouble reading for whatever reason, teachers do everything they can to help you with that important skill. If you struggle with math, teachers shrug and say "I guess you're not good at math." Which leads the child to believe that they're just "not good at math" for the rest of their life, and to stop trying.

My car (a VW) calls for higher octane gas. I usually get the medium grade (or silver at some stations). I asked the shop guys at the dealer what difference it would make to use a lower octane and they said one tank wouldn't hurt but by the second the engine would start knocking. So I grin and bear it.